SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: Rodbender on June 09, 2008, 02:14:43 PM
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I have a 78 Challenger with 460 & a Dominator jet. I am having problems with the boat overheating. Weird for a jet boat, but an issue never the less. The way the water system is set up now, I have a ball valve on the inlet from the jet that is open full, then I have 5/8 SS line that runs to the front of the motor then “T” off and ran to the water pump plate (inlet) right & left. Then from the manifold, I have a block off plate at the T-stat housing, but just below that is a ½ outlet that runs to the Bassett T valve, then to my twisties. Next to the ½ outlet is a 5/8 outlet that runs to the stern transom then is routed up to the front seat to a ball valve, then dumped overboard.
I guess the theory of the valve at the seat is to control the temp manually, but now I have it open full time and I am getting maybe1-2 lbs of water exiting the boat. The headers are working ok, but it does seem like I am getting too much water when running at 3k or so. At idle it seems to be trickling out of the dump, and when I am running about 3k out comes out better, but not much better. At 4 k the flow doesn’t increase and it temps up to 220-230.
I just recently pulled the motor and had to replace a few rods due to hydro locking from an intake leak. As freakish as it was, water rested on the intake and leaked down to 2 & 4. I pulled the freeze plugs and found the block packed with sand. I dug 98% of it out which was equal to a coffee can full of sand from both sides and some from the heads and re-plugged the motor. The heating problem was evident from before the rods, and seems to be getting worse now. When I put the head gaskets on, I made sure all the water jackets lined up and also the same for the new intake gaskets.
My next move is to pull all the lines off and make sure they are clear, then to disconnect and plug the header lines and remove the freeze plugs and flush the motor out with a hose while NOT running. My question to you is this, what is the possibility of the jet not producing pressure for the inlet, yet the boat seems to drive and plane fine? Could it be cavitating at the inlet? If not, what do you suggest that I try next?
:banghead:
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The first thing I would try is to make sure the lines themselves are not plugged, especially the tee, the tee actually has a separator inside it if its an actual marine inlet water tee, sounds to me like a major restriction that needs to be found.
Also check and make sure the small fitting on the jetpump is not plugged with crap, that is a very small hole.
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it seems as if the hose might be to small, i have 1" lines all the way from the jet to the motor to the headers
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it seems as if the hose might be to small, i have 1" lines all the way from the jet to the motor to the headers
1' is fine i'm running 5/8
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what kind of valving are you guys using? I am pretty sure there is a restriction, but the lines are way different from my other boats. Are you running pressure reliefs?
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I had this same problem before on my old ride and what I did was take that valve up front completely out, I dont like water running up and down the length of the boat personally. Then we back flushed the whole engine and the amount of sand that came out was crazy. Once we did that, the overheating issue went away. Looks like you are going in that direction as well. Good luck!
Chris
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rodbender , very unusual for a jet boat to run hot ,is this all the time ? or at idle etc . First verify the actual temp, if you can borrow a infa red "point and shoot" thermometer and check the fronts of the heads if you need help diagnosing this call me ! Tom
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im not running a pressure relief valve. i have a Lowes brass "t" that has 1" push on fittings in and i have no problem, alot of water comes out of the headers on the trailer but no over heating, and the motor just shit out with a spun rod bearing and i drove it for the whole weekend up at lake san antonio with about 10 psi of oil pressure at WFO, still runs and never got hot. Good luck, my .02 is keep it as simple as possible and there is no need for a $100 valve
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im not running a pressure relief valve. i have a Lowes brass "t" that has 1" push on fittings in and i have no problem, alot of water comes out of the headers on the trailer but no over heating, and the motor just shit out with a spun rod bearing and i drove it for the whole weekend up at lake san antonio with about 10 psi of oil pressure at WFO, still runs and never got hot. Good luck, my .02 is keep it as simple as possible and there is no need for a $100 valve
If you get the valve from the marine shops you'll pay out the ass for them, but from McMaster Carr they're about $50. Part #9763K12 from McMaster Carr. http://www.mcmaster.com
With a relief valve and 2 dump lines from the motor you can run the water wide open, eliminating the chances of getting hot spots in the heads. However, your motor will run too cold like that and you'll need a thermostat to get it up to 140*. But the beauty of this setup is that your temperature doesn't rise and fall with pump speed like it does with the gate valve.
For header water, plumb one of the fittings on the water crossover on the intake manifold to a gate valve, and the other side of the gate valve to your Bassett T valve. 5/8" in, 5/8" out. With this setup you solve the problem of fluctuating temperature/shock cooling and water in the oil.
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When I put the head gaskets on, I made sure all the water jackets lined up and also the same for the new intake gaskets.
I just read this part and it got me thinking. It is possible to install the head gaskets backwards and still have them line up with the water jackets on a Ford. However the engine would overhead due to the water not circulating properly. Ford have a front and a back to their gaskets.
Now heres how you tell if the head gaskets are installed correctly (without tearing the engine down).
If the head gaskets are installed properly you will be able to see the square corner of the head gasket poking out from between the head and block like this on both front corners.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2FDSCF04241.jpg&hash=652666f8c540e6be490fcbcb34b00293bdfb76ae)
Both back corners will look like this because the rear corner of the head gasket is rounded. (note that no head gasket is visible)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi147.photobucket.com%2Falbums%2Fr319%2Fjetboatperformance%2FDSCF04231.jpg&hash=830ed0abfe442d4087fe3d2447584335044718a3)
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Thanks guys and i will check out the gaskets just to be sure, but i think i found my problem. After back flushing the motor, clearing all the lines, and still scratching my head, i remembered that when i swapped carbs, i never cjhecked the jetting. i pulled a plug and they were white. I should have the carb back from PC in Ontario today and i expect this to solve the problem. It also might explain why i was getting such great gas milage!
i will keep you posted~
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But even still with the plugs showing lean, the cooling system should have been able to handle it. You still have a flow issue IMHO.
I also had an issue with flow at the upper RPM to the left head. I was running a single 5/8ths line to a regulator, Y'ed off to each side (log, head, then block and out to risers), and using 5/8ths all the way.
The regulator was killing me, it couldn't flow enough. It was fine at lower rpm, but once the pressure really kicked up, the regulator couldn't handle the GPM required. I removed the regulator, now I have 17PSI at WOT (if the outlet is bigger and can outflow than the inlet, you don't have to worry about block pressures). I think you don't have big enough lines (and /or there is a kink or blockage), esp with the overboard dump.
I suggest you go to Home depot / ace / osh / etc and get a house pressure gauge that goes to 200 PSI (they cost around 10 bucks) and plumb it in at the jet engine feed or nearby before any other valve, regulator, etc., then just start getting pressure readings at different places to figure out where the stoppage is.
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As for the carb, lean is an understatement. The carb that i put on was set up for a 350 crate motor. Dude at PC said himself that re-jetting should solve the heating. \
After taking all my hoses off and making sure they were clear, I re-installed them and hooked a hose to the inlet at the jet. Then disconnected the headers and capped it off at the mainfold. As i ran water thru the motor it seemed to flow fine. I did however re-routed the dump so it was just going overboard instead of running to the front seat ball valve and overboard.
As i said before, when i pulled the motor i opened up the freeze plugs and found the motor packed with sand. i cleaned it all out real good as well.
What makes me think that it is all carburation is that when i bought the boat it had a 830 holley on it. the secondariy pump was frozen and the carb was in bad shape, but i ran it and I didnt have a heating issue. It wasnt until i dropped the motor, fixed the rods, cleaned the sand out, and installed the new carb did it start heating up. This leaves me with three possible scenerios.
1) The head gaskets are on worng. (I will check those tonight when i get home)
2) The carb is the culpret and that will fix it self when i put the re-jetted carb back on.
3) There is a blockage in the motor. (But i flushed it out already and was clear)
:banghead:
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Did you notice a significant RPM difference between the new and old carbs?
A carb jetted for a 350 is not going to be that much different than one jetted for a 454, esp when you are talking a vac secondary 750. However, if the coolling system is right on the edge (or tuned) to get a specific temperature out of it, then changing the jetting could put it over the edge. If you are getting good mileage and the engine runs well otherwise, you may want to try just bumping up the secondary jets.
Look for an intake leak too (use carb cleaner to see if rpm changes when you spray it around). An intake leak can cause a significant rise in temp. But, either way, you are looking at it one at a time, and that is the right way to go.
Did the valve you took out have any kind of buildup or restriction internally?
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No, the valve was clear, but by by-passing it i was able to cut off 12" of hose and (2) 90 degreee fittings, needless to say they were 1/2".
When i talked to the dude at PC Carbs he said that there is a huge difference in the way you set up a jet boat vs a car, and that the 460 will require much more fuel than the crate 350. Since carbs are pretty greek to me, i guess i will know when i float this week.
i just checked the head gaskets and they are on right, but i am really glad for that post because that was in the back of my mind and i didnt want to pull the he4ads to find out! Thank you!
If this doesnt do the trick, my next step is to pull the freeze plugs and douche the motor just like before and see if there is a blockage. I took out a coffee can of sand before, I cant imagine that it is full again after only a few short trips.
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Did you notice a significant RPM difference between the new and old carbs?
A carb jetted for a 350 is not going to be that much different than one jetted for a 454, esp when you are talking a vac secondary 750. However, if the coolling system is right on the edge (or tuned) to get a specific temperature out of it, then changing the jetting could put it over the edge. If you are getting good mileage and the engine runs well otherwise, you may want to try just bumping up the secondary jets.
Look for an intake leak too (use carb cleaner to see if rpm changes when you spray it around). An intake leak can cause a significant rise in temp. But, either way, you are looking at it one at a time, and that is the right way to go.
Did the valve you took out have any kind of buildup or restriction internally?
As soon as i put the carb on, i will check that as well!
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Quick update on the carb.
i just got it back from PC. They bumped the jetting from 71 to 76 & 80 to 83. Is this significant to cause a heating issue?
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Quick update on the carb.
i just got it back from PC. They bumped the jetting from 71 to 76 & 80 to 83. Is this significant to cause a heating issue?
Yea, that is a pretty significant bump in jetting. A std 750 DP has 71's in the primaries, and 80's in the secondaries so you were at stock jetting (there is only one PV in the primaries so the secondaries need to be jetted up to compensate).
What size ca are you running? The duration at .050 has more to do with fuel jetting requirements than CID.. I will assume they asked you about your cam duration.
Upping the hose size and reducing the length = more flow. Those 90 degree fittings are really resrictive too, esp if internally there is a straight drill line with no chamfering.
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What size ca are you running? The duration at .050 has more to do with fuel jetting requirements than CID.. I will assume they asked you about your cam duration.
That is the one thing i didnt know about the motor, but i expect it to be a small leap over a RV cam. Nothing remarkable at all so i am sure it is close now.
As i put the carb on last night i re-tourqued the intake down and found that 4 of the bolts were hand loose. In addition to that, the mid plenum gaskets were shot so i replaced them as well. I am pretty sure it was sucking air at the intake in one spot or another. I will run it tonight and further check for leaks, and i may just R & R the intake gaskets to be sure.
I spoke with Tom last night about this problem and he seems to think that i may need to replace the wear ring in the jet as it may be a pressure issue. GREAT! so much for a turn key boat.... I should have known better. The jet seems good though, it tops out at 5k RPM, comes out of the hole great with no cavitation from idle to WOT. I guess time will tell!
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Cross your fingers Bro maybe it was/is just "leaning out" :banghead: Tom
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I have an update to the heating issues.
Dropped in Wednesday night in Topoc and ran for a while. It was still heating a bit at higher RPMs so i backed the timing off a little and that cured the problem while running. but at aidle, i am still heating and i have very little flow from the dump. Other than that, the boat ran great. Still looks a tad lean, but ran good never the less.
Before i jump into the jet, i will pull the freeze plugs and flush the motor real good to make sure I dont have a restriction. The jet feels weak, but i have had worse and they didnt heat up like this.
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If youre running a gate or a ball valve between the pump and the motor try opening it up a little more.
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Maybe try removing the bowl on the pump and check if it is obstructed from the other side of the inlet.
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Maybe try removing the bowel on the pump and check if it is obstructed from the other side of the inlet.
Oh Shit (no pun inteded). But the above post sounds like some sort of deep cavity search.
Sorry off topic.
T.J.
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Oh Shit (no pun inteded). But the above post sounds like some sort of deep cavity search.
Sorry off topic.
T.J.
ooops!! Can't type for shit sometimes!
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The ball valve is wide open.
I took the bowl off and the inlet is clear.
Tom seems to think that the wear ring is bad. Call me ignorant, but at WOT i should have a pretty big stream of water dumping out, and i dont. I have a mild stream, and at idle, it is just a slow garden hose stream. i guess i am having a hard time understanding how the wear ring will effect the water flow at WOT. i can see it at idle, but at 5k RPM and i am scooting across the river at 50+ MPH, the problem should be solved, Right??? i mean, there is a ton of bowl pressure at WOT.
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and your sure there is nothing blocking the intake even partially?
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and your sure there is nothing blocking the intake even partially?
Nothing blocking the lines, and i am sure the intake gasket is on right.
:screwy: :screwy: :banghead:
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The ball valve is wide open.
I took the bowl off and the inlet is clear.
Tom seems to think that the wear ring is bad. Call me ignorant, but at WOT i should have a pretty big stream of water dumping out, and i dont. I have a mild stream, and at idle, it is just a slow garden hose stream. i guess i am having a hard time understanding how the wear ring will effect the water flow at WOT. i can see it at idle, but at 5k RPM and i am scooting across the river at 50+ MPH, the problem should be solved, Right??? i mean, there is a ton of bowl pressure at WOT.
Right, but engine water is derived from suction pressure. If too much water blows past the wear ring that will drop suction pressure. I have to say I agree with Tom on this one.
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Right, but engine water is derived from suction pressure. If too much water blows past the wear ring that will drop suction pressure. I have to say I agree with Tom on this one.
Not 100% accurate, but really close, the cooling water actually comes from the centrifugal force/pressure of the impeller spinning around, and if the wear ring were worn/loose the backpressure would be "diddly squat" because the backpressure just gets pushed through the wear ring back to the inlet of the impeller.
Basically you are correct, the water does come from the "back side" of the impeller but not the "suction" side.
Broken down there are four different pressures on a Berkeley, Dominator, AT pump;
1. Suction pressure, it is exactly what it sounds like, but if the boat travels fast enough and things are working really well this area (in the suction piece of the pump) this becomes positive.
Lowest
2. Back pressure, again exactly what it sounds like, anytime something spins there is centrifugal forces that fly outward, this is after the inlet side of the impeller, but before the outlet. (see drawing).
Second lowest.
3. Pre stator pressure, or impeller outlet pressure, this is what you would measure whats in the bowl before the stator.
Highest
4. Pump outlet pressure this is the water pressure available to go to the nozzle and push the boat.
Second highest. (seems wrong, but is right)
[attachimg=#]
Hope this answers more questions than it asks!
Spent a lot of time playing with pumps to better regulate the amount of water pressure used for cooling. You actually can really change the pressure and volume by changing the eliptical shape of the depression.
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Not 100% accurate, but really close, the cooling water actually comes from the centrifugal force/pressure of the impeller spinning around, and if the wear ring were worn/loose the backpressure would be "diddly squat" because the backpressure just gets pushed through the wear ring back to the inlet of the impeller.
Basically you are correct, the water does come from the "back side" of the impeller but not the "suction" side.
Broken down there are four different pressures on a Berkeley, Dominator, AT pump;
1. Suction pressure, it is exactly what it sounds like, but if the boat travels fast enough and things are working really well this area (in the suction piece of the pump) this becomes positive.
Lowest
2. Back pressure, again exactly what it sounds like, anytime something spins there is centrifugal forces that fly outward, this is after the inlet side of the impeller, but before the outlet. (see drawing).
Second lowest.
3. Pre stator pressure, or impeller outlet pressure, this is what you would measure whats in the bowl before the stator.
Highest
4. Pump outlet pressure this is the water pressure available to go to the nozzle and push the boat.
Second highest. (seems wrong, but is right)
(Attachment Link)
Hope this answers more questions than it asks!
Spent a lot of time playing with pumps to better regulate the amount of water pressure used for cooling. You actually can really change the pressure and volume by changing the eliptical shape of the depression.
Right thats what I was trying to say. Injured my wrist a couple days ago and have to type with 1 hand plus Im all spun on Norcos at the moment. Great explaination of that though.
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Want to share? >:D
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One more random thought, what kind of grate are you running? Certain grates can multiply a wear ring issue by causing higher (numerically lower) suction pressures. Sorry thats the OCD in me. ::)
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It is a stock grate.
This is starting to make more sense to me now. I have searched hi and low not because i dont believe what you all have told me, but more so because it has to make sense to me before i start throwing my check book at it. Between your last post, and the fact that the boat seems to be lacking in power and plane-ability, and that nasty little rumble i get when the boat is fired up on the trailer, I know what i have to do. I will keep you all posted as i dive into the jet!
Thank you all for your help!